As always, the opposite of Chaos is, in fact, Order, especially as shown in the Mirror Realm involving Mirror Drakath and his friends, the Lords of Order.

Also, as revealed by the Void Larva NPC in the Void, as well as the Great Void Dragon itself, the closest magic related to Chaos magic is Void magic - which is exactly why the Void Dragon entrusted the Lords of Chaos with four different colored Void Spheres needed to unlock the door to its lair.

As revealed on the Chaos Shaper class description, as well as the Supreme Commander armor descritpion in HeroSmash, Chaos is actually neither good nor evil; it is a neutral commanding force that can be harnessed by heroes and villains and neutral characters alike.

The First Knight of Chaos, Exos (made a deal with Drakath about his desire to become a Chaos Lord; however, instead of becoming a Chaos Lord, he became Chaos Knight after being killed by The Hero and revived by Drakath)

Edvard (was promised Chaos powers by Wolfwing if he finished off the players, murdered Safiria, placed the blame for her death on the Lycans, and threw both species of Darkovia in an even deadlier war than the one they were in at the time)

King Alteon the Imbalanced (his plans involve Chaos, and in his second appearance, he says the Celestial Dragon Egg was a gift from Drakath - not the armor-clad half-wit as he called him from the Mirror Realm, the one from the main universe)

Zahart (controlled Tibicenas until the ring was destroyed)

Kezeroth (allowed the ChronoCorruptors to freeze him in time for another 26,000 years so he could get a second chance to unleash Quetzal upon Lore)

Nulgath (his plans also involve Chaos, and he planned to combine the Chaotic forces from Oversoul with the Chaos he found on Lore; his plan was accidentally interrupted by Beleen, who became Chaos Queen Beleen and bewitched him, turning him into a chibi-fied version of himself)